This disclosure relates generally to high temperature application, and more particularly to a system and a method for controlling a flow rate ratio in a high temperature environment.
In a high temperature environment, when fluid or gas properties are difficult to ascertain (for example, in the case that fluid or gas comprises multi-components) but an accurate flow split is required, it is usually impossible to measure flow rate of individual splitting flows by using flow meters, which results from complex fluid or gas properties. Because under the high temperature environment, a density of fluid or gas having complex properties depends on its temperature, pressure and composition, and the changes of fluid or gas on its temperature, pressure and composition in turn have an important influence on a flow rate of fluid or gas. So it is difficult to determine a flow rate ratio in such a circumstance.
For example, in a high temperature fuel cell system, especially hybrid system with gas turbine, or gas engine, fast load transition and optimization of system efficiency are one key issue. A traditional way of controlling a recycle flow rate in the high temperature hybrid fuel cell system is generally by adjusting a gas driving device of the system, such as a blower or a compressor. However, it is slow due to the redistribution of pressure in a recycle loop of the high temperature hybrid fuel cell system. Furthermore, the fluctuation of differential pressure at an anode inlet of a fuel cell may affect durability and even its lifetime of the fuel cell, and the recycle flow rate may affect fuel utilization of the fuel cell and even the system efficiency. But in operation of the conventional high temperature fuel cell hybrid system, the differential pressure at the anode inlet of the fuel cell and the recycle flow rate cannot be controlled separately, due to lack of real time measurement and control of recycle flow rate ratio.